Abrasive polishing wheel and element



Nov. 6, 1956 F. E. HENDRICKSON ENT ABRASIVE POLISHING WHEEL AND ELEM 2Sheets-Sheet 1 Filed Oct. 26, 1953 m T m W F RITZ E. Henomcxsou Nov. 6,1956 Filed Oct: 26,- 1953 F. E. HENDRICKSON ABRASIVE POLISHING WHEEL ANDELEMENT 2 Sheets-Sheet 2 INVENTOR. FRITZ E. HENORICKSON United StatesPatent 2,769,285 ABRASIVE POLISHING WHEEL AND ELEMENT Fritz E.Hendrickson, South Elgin, IIL, assignor to Norton Company, Troy, N. Y.,a corporation of Massachusetts Application October 26, 1953, Serial No.388,308

4 Claims. (Cl. 51-1935) This invention relates to improvements inpolishing wheels, and more particularly to a flexible, abrasivepolishing wheel element and to a method of making the same. Previousconstructions of devices for polishing work pieces, particularly pieceshaving contoured shapes, have been subject to certain disadvantages.These devices include solid wheels formed entirely of abrasive materialor wheels having abrasive peripheries. Most of the devices have utilizedabrasive surfaces having straight line or flat area contact with thework piece. In operation, an operator manually turns the contoured pieceat various angles in an attempt to bring all the surface areas thereofinto contact with the moving abrasive polishing surface. As a result,the polished piece either has some inaccessible and unabraded areas ornumerous areas abraded in different directions effecting an unsightlyappearance.

To overcome some of the foregoing disadvantages, use has been made oftravelling flexible belts having an abrasive face. Limited contouring ofthe belt face has been possible by engaging contact wheels with certainportions of the belt to efiect a desired cross-sectional shape. Someadditional deformation of the flexible belt has been possible by forcingeither the belt against the work piece or the work piece against thebelt. As a result, portions of the belt are overstressed therebymaterially shortening its working life. In addition, the variable andexcessive pressures exerted against different portions of the beltsurfaces quickly result in glazing caused by a filling or loading of thespaces between adjacent particles of abrasive material. These glazedsurfaces damage the Work piece either by streaking or burning thesurfaces thereof and may, if the wall of the work piece is sufiicientlythin, result in deformation through the inadequate dissipation of theheat so generated.

In the operation of abrasive devices where excessive pressures areapplied, lubricants such as water, oil, grease or the like are used towash away material being removed by abrasion and to absorb and conductheat from the work surface.

The device of the present invention is designed to eliminate theforegoing objections and disadvantages by the even distribution ofpolishing pressure over a contoured surface and by the quick dissipationof friction [heat through proper ventilation. Generally, this isaccomplished by presenting in wheel form the marginal edges of folded,flexible, abrasive-surfaced sheets against a work piece and effecting abending of small marginal areas of the folds to provide a multiplicityof abrasive surfaces by rotating the wheel and moving the folded sheetsover the work surface or surfaces to be polished.

An important object of the invention, then, is to provide a novelpolishing Wheel element anda method of contoured Work surfaces Withoutthe application of excessive pressures.

2,769,285 Patented Nov. 6, 1956 Still another object of this inventionis to provide, in a flexible polishing wheel, a multiplicity of smallabrasive areas for contact with a surface to be polished.

A further object of this invention is to provide a polishing wheelhaving flexible elements which operatively engage a contoured worksurface under a uniformly distributed pressure.

A still further object of this invention is to provide flexible elementsin a polishing wheel having incorporated therein a highly eflicientventilation system.

Another and still further object of this invention is to provideflexible elements for a polishing wheel having uniform polishingcharacteristics throughout the entire work life thereof.

Yet another object of this invention is to provide a polishing wheelhaving elements which are self-cleaning in operation.

A still further object of this invention is to provide elements for apolishing wheel which are simple and durable in construction, highlyefficient in use, and inexpensive in maintenance and operation.

Other and further objects of the invention will become apparent to thoseskilled in the art from the following detailed description of theannexed sheets of drawings, which disclose preferred embodiments of theinvention.

On the drawings:

Figure 1 is a face view in elevation of an abrasivecoated polishingsheet before being folded along the dotted lines;

Figure 2 is an edge view of a polishing sheet folded as suggested inFigure 1;

Figure 3 is a face view in elevation of the folded polishing sheet shownin Figure 2, in which adjacent folds partially overlap;

Figure '4 is a front view in elevation of a composite pluralelementpolishing wheel constructed according to the principles of the presentinvention;

Figure 5 is a vertical cross-sectional view, with portions in elevation,taken along a plane indicated substantially by the line 55 of Figure 4and showing details of construction of a wheel hub assembly on which thefolde abrasive sheets are mounted;

Figure 6 is an enlarged edge view in elevation of a foldedabrasive-coated polishing sheet as seen along that portion of theperiphery of the wheel indicated by the line' 66 of Figure 4 and showingthe numerous marginal edge portions bent along the wheel periphery toform abrading areas;

Figure 7 is a modified form of polishing sheet showing the provision ofrows of slits provided to facilitate the bending of the marginal edgeportions thereof;

Figure 8 is a view, similar to Figure 3, of a modified form of sheet inwhich adjacent folds completely overlap; and,

Figure 9 is a View, similar to Figure 2, showing the width of the foldedsheet in Figure 8 as being the width of a fold.

As shown on the drawings:

Referring now'in detail to the several figures, the numeral 20 generallydesignates a sheet of fibrous material such as paper, cloth, or thelike. A coating 21 of granular mineral substance, such as emery or otherabrasive, is applied and adhesively secured to the sheet. For maximumefficiency, both faces of the sheet are so coated.

However, the herein described invention will function s at isfactorilyif but one face of the abrasive sheet is so coated.

In the preferred form as shown in Figures 1, 2 and 3, theabrasive-coated sheet 20 is folded along the dotted fold lines 22, 22.The fold arrangement is such that one pleat partially overlaps anadjacent pleat effecting a folded sheet of a width narrower than theunfolded sheet. As

so folded, the sheet is doubled upon itself along the fold line 23extending medially lengthwise thereof. In this folded and doubledarrangement, each of the ends of the sheet present an undulated edgeoutline having a Wavy form with successive curves in alternatedirections, as seen in Figure 6. While the abrasive-coated sheet ispreferably rectangular in shape it may be of any form folded or bunchedto present a wavy periphery. Also, each abrasive element may compriseany desired number of thicknesses of abrasive coated sheets in faceengagement or interleaved with uncoated sheets. As so folded, eachabrasive-coated sheet is applied to a central mounting or driving hubconstruction 24.

It is to be understood that the mounting hub construction shown is forpurposes of illustration only as many other forms of construction areequally applicable.

As shown in Figures 4 and 5, the hub 24 has face plates 25 and 26centrally apertured as at 27 for mounting on a drive shaft 28. The driveshaft has a reduced end portion 29 terminating at one end in an abutmentshoulder 30 and at its other end in a threaded portion 31. A sleeve 32embraces the shaft portion 29 between the face plates to maintain theplates in desired spaced relation. A nut 33 is threaded on the shaft andserves to clamp together the hub assembly.

A group of mounting pins 34, 34 are fixedly secured to one of the faceplates, shown herein as the plate 25. The pins are spaced around acircle located between the center and periphery of the face plate.Openings 35, 35 are provided in the other face plate for slidinglyreceiving the pins therethrough. By this construction, the pins preventrelative rotary movement between the face plates and each form a carriersupport for a folded polishing sheet.

As best shown in Figure 4, each folded sheet 20 is looped around amounting pin with the ends of the sheet coextensively extending radiallyoutward of the hub. As many folded sheets are applied as there aremounting pins to complete the polishing wheel. The entire periphery ofthe wheel is thereby made up of the ends of sheets each presenting awavy or corrugated shape, the waves or corrugations of adjacent endsslanting in opposite direction. Pockets 36, 37, 38 and 39 are therebyformed in the folded arrangement of each sheet. The pockets 36 and 39face each other and are open along their length from the mounting pin tothe periphery of the wheel. Similarly, the pockets 37 and 38 are openalong their length but extend away from each other. During the rotationof the polishing wheel, the resulting centrifugal force effects aconstant flow of air radially outward of the wheel through the pocketsthereby providing highly efficient ventilation.

When the periphery of the rotating polishing wheel engages a work piece40, shown in dotted lines in Figure 4, certain of the marginal edges ofthe folded sheets are permanently bent generally normal to theiroriginal positions. This is diagrammatically shown in Figure 6. It willbe noted that there is thereby provided numerous small abrasive areasfor engaging a surface to be polished. These areas are on opposite sidesof each loop which generally bend as at 41 and 42 away from thedirection of rotation of the wheel. It will be noted that the portions41 and 42 turn and expose, outwardly of the polishing wheel, oppositesides of the abrasive sheet. The portions so bent usually are of amaximum width of A; inch to A1. inch and of a length dependent on theperipheral length of the sides of the pocket. As the bent portions arerelatively narrow for their length and are supported by the flexiblebody of the sheet, they become selfadjusting to completely engage acontoured surface under a minimum of contact pressure and thereby areself-cleaning of any material removed from a surface during thepolishing operation. Consequently, any heat generated by friction isminimized and is quickly dissipated by the improved ventilationpreviously described. As a result, only occasional lubrication of theabrasive surfaces is necessary and the possibility of glazing iseliminated.

It has been found in the operation of such a polishing wheel that theresistance to bending of the marginal edges is dependent on thestiffness of the abrasive sheet. To facilitate the quick bending asdesired, rows of short slits 43, 43 may be provided as shown in Figures6 and 7. Generally, the slits are located in the pleat areas of thesheet preferably at or near the initial point of contact with the Workpiece surface. Should the abrasive sheet be relatively flexible, slitsonly along the peripheral edges of the pockets are necessary anddesirable. As many edge slits as desirable may be provided. If, however,the sheet is relatively stifl and resistant to bending, then longerslits or rows of spaced slits are provided as shown. In any event, whenslits are provided they should start along the initial working edge ofthe pleated or bunched sheet. In addition, the slits may be located inalignment lengthwise of the sheet or in staggered relation.

Shown in Figures 8 and 9 is a modified form of sheet 200 having anabrasive coating 21a. In this form, the pleats 44, 44 completely overlapeach other to effect a folded sheet of the width of a single pleat.Before being mounted on a wheel the sheet is folded medially upon itselfas at 23a. With this type of folded sheet, a wheel having the width ofone pleat may be formed by mounting a single sheet on each mounting pin,or, a wheel of any desired width is possible by mounting folded sheetside-by-side on a mounting pin. In this form of construction, theabrasive working areas 45, 45 are bent from the sides of the pleats. Asin the previously described form of sheet construction, bending slits 46may be provided. Here, the slits are preferably located centrally of thesides of the pleats and/or at the bottom of the pockets.

With the several forms of folded abrasive-coated sheets shown anddescribed herein, it has been found under certain conditions to bedesirable to provide uncoated spacer sheets 47, 47 in the pockets toseparate adjacent coated surfaces and thereby prevent rubbing withresulting loss of abrasive material. Such spacers are shown in Figure 6.This provision is equally applicable to the form of folded sheet shownin Figure 9.

By the features described hereinabove, there is provided a polishingwheel having an effieiently ventilated and self-adjusting contact underrelatively light pressure with the surface of a work piece to bepolished. The result is to reduce the costs of operation by minimizingmaintenance through replacement of abrasive sheets and by extending theworking life of the wheel while at the same time effecting a completepolishing of surfaces, both flat and contoured, in one direction whichis of pleasing appearance to the eye.

It is to be understood that the forms of the invention, herewith shownand described, are to be taken as preferred embodiments of the same, andthat various changes and modifications in form and structure may beresorted to without departing from the spirit of the invention or thescope of the appended claims.

I claim as my invention:

1. A coated abrasive element adapted for use in an abrasive Wheel whichcomprises: a flexible backing member; an abrasive coating bonded to andsubstantially uniformly covering at least one side of said backingmember; and a plurality of relatively rigid pleats in said backingmember, said pleats at least partially overlapping one another andhaving the outer edges only thereof adapted to be bent angularlywithrespect to the pleat to provide a plurality of narrow abradingsurfaces when said element is positioned in an abrasive wheel andcontacts a work piece.

2. A coated abrasive element adapted to be radially mounted from the hubof an abrasive wheel which comprises: a flexible backing member; anabrasive coating substantially uniformly covering at least one surfaceof said backing member and bonded thereto; a plurality of fold lines insaid backing member, said fold lines extending outwardly from said hubwhen said element is mounted in said wheel to define a plurality ofrelatively rigid overlapping pleats; and a plurality of narrow abradingsurfaces angularly inclined to said pleats and formed at the outer endonly of said pleats by bending of said backing member along said foldlines upon contact of said element with a work piece.

3. In a coated abrasive wheel having a central hub and mounted meansassociated therewith: a plurality of coated abrasive elements radiallydisposed about said hub and held thereto by said mounting means, saidcoated abrasive elements each comprising at least one sheet of flexiblematerial having a substantially uniform abrasive coating bonded on atleast one side thereof, said sheet being pre-folded prior to mounting onsaid wheel to provide a plurality of relatively rigid overlappingpleats, said pleats extending from said mounting means to the outerperiphery of said wheel and having the outer ends only thereof adaptedupon contact of said element with a work piece to form angularlydisposed narrow abrading surfaces which extend at an angle to thedirection of rotation of said wheel.

4. A coated abrasive wheel having a central hub, mounting meansassociated therewith, and a plurality of pleated elements having acoating of abrasive firmly bonded thereto, said elements being radiallydisposed about said hub and held thereto by said mounting means,comprising: a peripheral face extending about said hub and locatedradially outwardly therefrom, said peripheral face being composed of aplurality of relatively narrow abrasive flaps extending generally acrossthe peripheral face, said flaps being angularly bent extensions ofrelatively rigid pleats, said pleats being formed in said element andextending from said flaps to said mounting means.

References Cited in the file of this patent UNITED STATES PATENTS1,819,171 Hopkins et a1 Aug. 18, 1931 1,882,769 Bugg Oct. 18, 19321,897,971 Johnston Feb. 14, 1933 2,226,624 MacFarland et a1 Dec. 31,1940 2,290,236 Hall July 21, 1942 2,574,037 Hendrickson Nov. 6, 19512,581,411 Hendriekson Jan. 8, 1952

